This invention relates to photographic composing apparatus, and more particularly to apparatus for projecting the selected characters upon a sensitized material.
A necessary function of such apparatus is to cause relative motion between the projected character images and the sensitized surface. This motion usually depends upon the widths of the characters and upon the increments to be added between words and characters to justify the line. This motion must also be performed with speed and precision commensurate with the desired accuracy in the alignment of character projections.
Early in the development of photocomposition, the optical system used for character projection was held stationary, and the carriage on which the sensitized material is mounted was moved at discreet times, both to bring about spacing between successive projected characters and words, and to bring about spacing between successive lines, or line spacing.
Thereafter, U.S. Pat. No. 2,670,665 which issued Mar. 2, 1954, proposed a very practical character spacing arrangement wherein the character was caused to become collimated and then refocused by a decollimator which was positioned in the proper relationship to a sensitized sheet for producing the necessary spacing with respect to the prior character.
However, the development of character escapement thereafter appears to have abandoned the collimating teaching of U.S. Pat. No. 2,670,665 and taken the form of optical leverage devices. In optical leverage concepts, the rotating font and the sensitized sheet were both held stationary, and the image projection angle changed, or wherein the entire drive motor and rotating character font is stepped along relative to the sensitized sheet. Many proposals have been made, which include roof mirrors or prisms to pick an image from the disc font and space the resultant projection along the paper, and intercepting mirrors which are rotated in proper sequence to reflect the image. The proposal by U.S. Pat. No. 2,670,665 appears to have been abandoned for reasons unknown. The provisions of this invention may be the clue overlooked which enables the basic teaching of U.S. Pat. No. 2,670,665 to be of greater simplicity and more practical than many of the developments of that which came after the proposals of U.S. Pat. No. 2,670,665.